Limits...
Reactive Transport Modeling of the Enhancement of Density-Driven CO2 Convective Mixing in Carbonate Aquifers and its Potential Implication on Geological Carbon Sequestration.

Islam A, Sun AY, Yang C - Sci Rep (2016)

Bottom Line: We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing.The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system.Early saturation of the reservoir can have negative impact on CO2 sequestration.

View Article: PubMed Central - PubMed

Affiliation: Bureau of Economic Geology, The University of Texas at Austin, TX, USA.

ABSTRACT
We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing. The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system. The extent of convection is quantified in term of the CO2 saturation volume of the storage formation. Our results suggest that the density increase of resident species causes significant enhancement in CO2 dissolution, although no significant porosity and permeability alterations are observed. Early saturation of the reservoir can have negative impact on CO2 sequestration.

No MeSH data available.


Related in: MedlinePlus

Concentration maps of Ra = 10,000, homogeneous case; (a,c,e and b,d,f) show results of with and without reactions, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4837360&req=5

f6: Concentration maps of Ra = 10,000, homogeneous case; (a,c,e and b,d,f) show results of with and without reactions, respectively.

Mentions: Figures 6, 7, 8 plot concentration contours for the case of relatively high mean permeability 100 mD (Ra = 10,000). As expected, high permeability allows dissolving more CO2 and consequently reaction effects become more pronounced. Among three cases, the most intense enhancement is observed in heterogeneous reservoir where CO2 saturates completely in 500 years. Ra is high enough to initiate convection in early times and for heterogeneity the convection cells get more dynamicity because of availability of local high permeable favorable paths. Thus CO2 dissolution swells, transporting more CO2 saturated brine in contact with carbonates. The concurrent convection and reaction processes drive fast spreading of dense dissolved phase in the reservoir both laterally and downward. Figure 9 shows concentration profiles of Ra = 10,000. In this case layered heterogeneity adds little more reaction effect over the homogeneous distribution. For no reactions case maximum saturation obtained is ~40%. The early saturation due to geochemical effects has a negative effect on CCS in the sense that much injected CO2 may remain as completely undissolved. As a result, potential of leakage through high permeable zones or abandoned wells can be greater. To our best knowledge, no experimental results of convection enhancement due to geochemical reactions are reported. This strongly suggests a potential future research.


Reactive Transport Modeling of the Enhancement of Density-Driven CO2 Convective Mixing in Carbonate Aquifers and its Potential Implication on Geological Carbon Sequestration.

Islam A, Sun AY, Yang C - Sci Rep (2016)

Concentration maps of Ra = 10,000, homogeneous case; (a,c,e and b,d,f) show results of with and without reactions, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837360&req=5

f6: Concentration maps of Ra = 10,000, homogeneous case; (a,c,e and b,d,f) show results of with and without reactions, respectively.
Mentions: Figures 6, 7, 8 plot concentration contours for the case of relatively high mean permeability 100 mD (Ra = 10,000). As expected, high permeability allows dissolving more CO2 and consequently reaction effects become more pronounced. Among three cases, the most intense enhancement is observed in heterogeneous reservoir where CO2 saturates completely in 500 years. Ra is high enough to initiate convection in early times and for heterogeneity the convection cells get more dynamicity because of availability of local high permeable favorable paths. Thus CO2 dissolution swells, transporting more CO2 saturated brine in contact with carbonates. The concurrent convection and reaction processes drive fast spreading of dense dissolved phase in the reservoir both laterally and downward. Figure 9 shows concentration profiles of Ra = 10,000. In this case layered heterogeneity adds little more reaction effect over the homogeneous distribution. For no reactions case maximum saturation obtained is ~40%. The early saturation due to geochemical effects has a negative effect on CCS in the sense that much injected CO2 may remain as completely undissolved. As a result, potential of leakage through high permeable zones or abandoned wells can be greater. To our best knowledge, no experimental results of convection enhancement due to geochemical reactions are reported. This strongly suggests a potential future research.

Bottom Line: We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing.The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system.Early saturation of the reservoir can have negative impact on CO2 sequestration.

View Article: PubMed Central - PubMed

Affiliation: Bureau of Economic Geology, The University of Texas at Austin, TX, USA.

ABSTRACT
We study the convection and mixing of CO2 in a brine aquifer, where the spread of dissolved CO2 is enhanced because of geochemical reactions with the host formations (calcite and dolomite), in addition to the extensively studied, buoyancy-driven mixing. The nonlinear convection is investigated under the assumptions of instantaneous chemical equilibrium, and that the dissipation of carbonate rocks solely depends on flow and transport and chemical speciation depends only on the equilibrium thermodynamics of the chemical system. The extent of convection is quantified in term of the CO2 saturation volume of the storage formation. Our results suggest that the density increase of resident species causes significant enhancement in CO2 dissolution, although no significant porosity and permeability alterations are observed. Early saturation of the reservoir can have negative impact on CO2 sequestration.

No MeSH data available.


Related in: MedlinePlus